18 — TOOLING · 2026

Swing Set Design System

Seven AI-agent skills in six stages that turn a backyard, a budget and a reference photo into a build package, with a safety audit that can refuse to proceed.

Built: A chain of seven AI-agent skills that designs a backyard playset.
Stack: Agent skills backed by nine Python scripts; NDS 2018, ASTM F1148 and CPSC checks.
State: Done; two finished designs.

DONE · UPDATED 2 OCT 2026

Packaged as a plugin for my coding agents; two finished designs.

Carter Barnes · cloud engineer, federal Azure · Contact

Screen capture · The pipeline guide. The guide predates the seventh skill.

What it is

A seven-skill pipeline that takes a backyard, a budget and a photo you liked, and returns a complete build package: concept, structural sizing, an ASTM F1148 and CPSC safety audit that can refuse to proceed, a priced shopping list, a cut list and construction drawings.

I built the thing that designs playsets, then used it. Seven skills, each usable on its own, run in six stages (the last stage runs two: the build documents, then the write-up), and the output is something you can take to a lumber yard. Two finished designs came out of it, one a full build package with a cut list, hardware BOM, assembly sequence and PDF.

How it works

Inspiration: A structured brief from a reference photo: design language, material palette, what to steal, what to skip.
Concept: Name, silhouette, feature placement, siting and an ASCII layout.
Structural: Beam and post sizing to NDS 2018 ASD with a 1.5× dynamic factor and a safety factor of at least 1.5, plus footing and hardware schedules.
Safety: The gate: ASTM F1148 and CPSC use zones, fall zones, entrapment gaps, protrusions and surfacing depth.
Materials: Species and grade per member, fasteners, finish, and a priced list with waste factors and regional ranges.
Documents: Cut list, hardware BOM, assembly sequence, orthographic plates and a construction PDF, plus an interactive write-up.

By the numbers

7: chained skills, each usable on its own
1.5 ×: dynamic factor on every structural load
9: Python scripts inside the skills, from beam sizing and safety checks to the PDF
2: finished designs out of the pipeline

Decisions

01
Build documents don't run until the safety audit passes
Build documentation does not run until the safety audit returns a pass. Anyone can generate a plausible plan; the value is a pipeline that will refuse to hand you one.
02
Arithmetic goes in scripts, not prose
Beam spans and footing volumes go through Python calculators. The model's job is judgment and sequencing; the script's job is numbers. Mixing them is how you get a confident wrong answer about a beam someone swings from.
03
Skills fire mid-conversation
The structural and safety skills trigger on a passing question like 'will this hold?', because that is when people actually ask.
04
Inspiration and compliance are different jobs
The photo skill is explicitly not a compliance review.

What I learned

01
An honest estimate beats a fitted one
When a brief's budget sat below the materials floor for its feature list, the package said so and split the build into two phases instead of quietly cutting features.
02
The calculator changes the plan
The footing sizer put the A-frame piers at a safety factor of 1.36 at 10 inches. The package upsized them to 12 inches, about 1.96, for roughly $14.

What went wrong

01
The first design failed its own safety audit
The first pass of one design failed the gate twice: a 36-inch guardrail where ASTM F1148 calls for 38 inches, and a saucer swing that clashed with the A-frame. The audit also called 9 inches of wood fiber marginal under an 8-foot fall, and found rope-only access too hard for the youngest users, so a real stair replaced it. All four were fixed before the build documents ran.